PANCREAS. 



The pancreas in many respects resembles the salivary glands, though there are important 

 differences. It is lobulated, and has a connective-tissue stroma, blood and lymphatic 

 arrangements like the salivary glands. It is a compound tubular gland, and the gland-tissue 

 has lobar and inter-lobular ducts, which terminate by means of an intermediate piece in the 

 alveoli, which consists of wavy, branched, and convoluted tubes, each having a basement-mem- 

 brane lined by a single layer of columnar or cylindrical cells, whose free ends are sometimes 

 conical. The substance of each cell shows a marked division into two zones the outer 

 (next the membrana propria) is homogeneous, and stains easily and deeply with carmine and 

 logwood the inner is coarsely granular, and does not stain readily with dyes, and in it lies 

 the spherical nucleus. The lumen of the alveolus is small, and so are the alveoli themselves. 

 Heidenhain has shown that the appearances and relative sizes of these two zones alter during 

 digestion i.e. during physiological activity, just like the salivary glands. 



PREPARATION (a). Place small pieces of the freshly excised pancreas of a dog in 

 absolute alcohol for forty-eight hours, and then make sections. Stain them with carmine, and 

 mount in Farrant's solution, or, better still, with logwood, and mount in dammar. 



(b) Osmic acid preparations are also valuable. 



EXAMINATION (L). Observe the lobules, the connective sheath and its septa, perhaps 

 containing the section of a lobar duct. Study a lobule, and note an inter-lobular duct ; and 

 the alveoli relatively small cut in every direction. (H). Study an alveolus : note the 

 secretory epithelium, with its outer zone stained of a logwood tint, and its inner half granular 

 and unstained. This appearance is quite characteristic. Scarcely any lumen is observable, 

 and very little interstitial matter separates one secretory cell from another. (Indicate the 

 appearance of the alveoli, and the epitlielium lining them, in PI. XVI., Fig. 4.) 



